The present invention relates to bore sighting for firearms, and particularly to a device that aids in bore sighting procedures.
The prior processes involved for xe2x80x9csighting inxe2x80x9d a firearm typically involve the use of a target and live ammunition. While this process is typically satisfactory for the shooter, a considerable amount of time and a degree of expense are involved.
The above xe2x80x9csighting inxe2x80x9d process may not be available in certain situations. For example, a hunter may jar the firearm and upset the previous sight adjustments. The hunter may be in a situation where the typical process for xe2x80x9csighting inxe2x80x9d the weapon is not possible or advisable. This is especially true in situations where the discharge of the firearm could have a negative effect on hunting situations. Further, access to a proper target range is not always easily available. A need has therefore been realized for some form of sighting device that does not require discharge of live ammunition to at least initially accurately set the targeting sights of the firearm.
In response to the above need, various forms of xe2x80x9cborexe2x80x9d sighting devices have been developed. In the distant past, such sighting devices made use of incandescent-type lights. More recent developments, however, have lead to the use of laser sighting arrangements. Of these, numerous units are adapted for insertion at the muzzle end of the firearm. The use of a laser certainly increases the potential for accuracy. However, the mounting of a laser in the muzzle end of a firearm does not necessarily lead to an accurate representation of the path a bullet will travel to a selected spot on a target. A very slight misalignment of the laser beam from this point will result in huge magnification of the error at even relatively short distances.
Others have sought the solution of mounting a laser optical device within the firing chamber of a firearm. One such device is described in U.S. Pat. No. 5,787,631 to Kendall. This patent, while describing a substantial improvement over prior forms of optical bore sighting devices, included accuracy problems. The lens for the laser was provided separately from the laser module and could be subject to misalignment. The laser module itself, was adjustable by means of four set screws that were provided equally spaced about a transverse plane. These securing devices could be easily adjusted by the user with the end result being that the light beam could be easily adjusted to an angle different from the long axis of the insert. The insert was designed to simulate a particular firearm cartridge and, if accurately machined, would, upon loading in the firearm breach, would automatically become centered with the cartridge body axis coaxial with the axis of the firearm bore. A misadjustment of the set screws or even a temperature change or jolt could affect the mounting arrangement and cause misalignment of the laser beam, thereby negatively affecting the sighting performance of the device.
A need has remained for a firearm bore sight system that will maintain an accurate coaxial relationship with a firearm cartridge-shaped insert so that a light beam will be maintained in a coaxial relationship with a firearm bore so a reliable and repeatable identification can be easily and quickly determined for a bullet impact point. A dot of light, then, at a distance of, say, thirty yards, will reliably indicate that point as being along the axis of the firearm bore. This point can then be used to accurately gage and calibrate the external sighting device for the weapon.
A difficulty stemming from use of an adjustable bore sight of the type inserted within the firing chamber of a firearm, is that the beam generated by the optics must not impinge on the sidewalls of the firearm bore. If this happens, the beam becomes diffused and will not produce an accurate indication of the bore axis. Further, it is very difficult to withdraw the sighting unit and make adjustments that are meaningful. The typical casing is substantially cylindrical and can be rotated, either intentionally or unintentionally and this factor seriously affects any potential adjustments that might be made. A solution to this issue is to pre-calibrate the sighting device at the factory where the device is made. However, the adjustment screws allow for tampering and a slight misalignment of the device could lead to an attempt by the owner or operator to readjust the unit, thereby seriously misaligning the device and frustrating the intent to provide an accurate sighting device.
An object of the present invention is to provide a firearm bore sighting system which may be readily calibrated initially and then substantially permanently set in the calibrated condition for continued accurate usage.
Another objective is to provide such a device that includes adjustment and calibration features that operate on a complete module including lens so the beam produced by the beam-emitting device is consistent regardless of the adjusted position of the unit.
A still further objective is to provide such a device that may be utilized in different caliber firearms.
A yet further objective is to provide such a system that is stable and capable of withstanding normal wear and tear.
A yet further objective is to provide such a device that includes ready access to internal batteries.
These and still further objectives and advantages will become apparent upon reading the following description.